The invention relates to a nonskid body comprising a tread carrier secured to a basic body which is connected to the lower end of the stick of a walking aid via a ball joint whose hollow ball cup is situated in the axial central opening of a ring and is composed of supplementary sectional ball cup profiles at one end of the central opening as well as of a plug inserted at the front surface in the other end of the central opening and fixed in it, the ball having a shaft projecting out of the curved end of the central opening of the ring and being secured in a bore of a connecting piece.
In a known nonskid body having a ball joint (German Pat. No. 341 874) the ball consists of two semispherical cup portions urged by a spring into opposite directions. A shaft extending from the cavity of the one cup portion and through the opening of the other cup portion is connected to the basic body. The hollow ball cup for housing the ball is designed at one end of a sleeve and separated via a constriction from a cylindrical part of the sleeve secured to the stick.
It is an essential disadvantage of the construction that, when pressure is exerted vertically in downward direction on the stick its lower end moves downwardly relative to the ball thus causing the latter to spread the constriction of the sleeve so that the ball may be displaced upwardly in the sleeve. The ball loses its firm fit in the hollow ball cup and is no longer firmly supported in the enlarged hollow ball cup. Such a loose support of the ball in its socket is most dangerous for the user of the stick because the frictional connection between the stick and the nonskid body suddenly fails and the only loose relation between said elements may give rise to the escape of the stick in oblique direction and to a probable fall of the user of the stick. In addition, with such an oblique escaping of the stick the ball may come off the shaft; at least, cracks may be formed which, later on, may result in a break. It is also disadvantageous that by the lifting of the ball in the hollow ball cup, its inside is accessible to dust, dirt and water penetrating into the hollow ball cup and affecting the operation of the ball joint or even rendering it completely inoperative. In the course of time, due to dust and dirt, the ball and hollow ball cup surfaces will get rough and lose their sliding ability, while in frozen condition, water will damage or block completely the ball joint.
Furthermore, because of its design of deformable semicups and its fixture by screws with the carrier element, the nonskid body is not very robust. The assembly of the nonskid body and its connection to the stick and to the basic body are complicated and involved. A dismantling of the nonskid body for inst. for cleaning or for the exchange of pieces is not easily possible. Due to its construction, the price of the nonskid body is inappropriately high for the intended use.
The above disadvantages can be also met with the known nonskid body of the foregoing type according to British Pat. No. 13 73 593. In case of said nonskid body, the basic body connected to the tread carrier contains the bore for housing the shaft of a one-part ball, the ring supporting the ball forming the connecting element to connect the nonskid body to a stick. Thus, from the nonskid body the ball projects upwardly, and its support in the central opening of the ring is ensured by a plug, a Belville spring washer, a stopper and a rib. The tread carrier connected to the basic body consists of two elements movable relative to one another, of which one serves as a slide whose sliding surface normally projects beyond the flat nonskid surface of a braking member. Only with the increasing weight of the body supported by the stick, a spring is compressed between the slide and the braking member which is pressed out of the slide to prevent the stick from slipping away from the user. The only occasional antiskid effects of the known nonskid body rendering it unsuitable, for safety purposes, for a walking stick or a crutch, on the one hand, and its ball joint design does not offer the required safety for the intended purpose, on the other hand.
If a pressure in vertically downward direction is exerted on the stick, its lower end moves downwardly relative to the ball thus compressing the spring washer, while the ball is displaced upwardly in the central opening of the ring. The ball is deprived of its firm abutment against the sectional ball cup profile of the ring and its support in the spread apart hollow ball cup is not firm any longer. This may cause a sudden fall of the user because his stick may suddenly escape in oblique direction. The ball may come off the shaft or cracks may form at least which result in a later rupture. By the lifting of the ball in the ring the central opening will be accessible to the penetration of dust, dirt and water into the hollow ball cup and the ball joint may be damaged or rendered inoperative. The great number of constructional elements of the nonskid body contribute to its expensive manufacture and to the difficulty of exchanging or cleaning its elements.
Starting from a nonskid body according to British Pat. No. 13 73 593, it is the object of the invention to provide a nonskid body which is robust and whose ball joint connection with the stick of the walking aid will reliably withstand for a long time all forces developing in practice. In addition, by a simple construction it shall be producible at a reasonable price, its assembly and disassembly shall be easy and its design shall be robust.